rear differential diagnosis...

[McCoy]

Forgot how much fun it was to get the diff out... and how fun it is to pinch fingers under the diff, yeah.

Well, it wasn't so obvious once I got the diff out. I don't think it should be knocking this bad (see video), but then again it's been 3 years since I've had the diff out and don't really remember how much play there should be.

http://www.youtube.com/watch?v=7O70d_TaSOM

I don't think this last track day was the first time it's overheated...


The drain plug magnet is full of some very finite metal... more than last time I pulled it.


Before I pulled the HLSD.


pinion gear, no real wear that I could tell and no movement in/out or side/side.


The HLSD looks to be in good shape and the side bearings look to be in the same condition.


What else should I be checking here....

[marcinko]

Diffs usually get louder when you don't have fluid in them. The backlash looks a little loose in the video but is probably fine. Try using some Motul 90-PA diff fluid.

Just make sure when you put it back together that the spacers and everything go in the exact way they came out. Check the gears with a white grease or something to be sure the contact patch is right in the middle of the teeth when you are finished.

[McCoy]

Yes, it was full of fluid, I did drain it before dropping it.

Something is wrong for sure... if not, then the diff shouldn't be nearly on fire when I come off track, smoking out of the overflow tube for a good 20 minutes with the diff housing measuring close to 400F. Now it sounds like straight cut gears and whistles at highway speeds. At 5-10 mph you can definetly hear something going on back there (bearing wise) when giving it gas.

I was hoping to find a pile of bearings or something very obvious when I opened the case, but didn't...

[Dalspec]

I build R200s so thought I'd chip in.

A few things I'd look at:
1. Comparison of backlash, pinion pre-load and ring-gear run-out to the figures measured when it was last built. ie when the torsen/helical was installed. Are they similar or different?
2. If the figures aren't available I'd measure it and compare to factory tolerances (I can almost guarantee pinion pre-load will be loose and backlash wil have opened up).
3. Is there evidence of the side bearing races having spun up in the housing?
4. Do the side bearings turn freely without binding?
5. Does the pinion turn freely without binding?
6. Is there clear evidence of tooth heel wear (outside drive face)? ie bearing blue/paste not requried to show wear?

My first guess (without more info), is pinion or side bearing bearing failure. As the bearing(s) fail the pinion and ring gear are allowed to walk away from each other. The teeth subsequently engage differently and results in whining under accel and decel and clunking on/off gas. Both get worse the longer it is left.

Replacement of both front bearings or the offending side bearing stops the clunking and whine if caught early enough. If not the whine remains, albeit lessened, as the wear pattern has changed.

More often than not, the ones I come across are bin jobs as 200s are cheap (here in Perth anyway), so it's more cost effective to transfer a centre to a new donor diff than replace bearings (Donor diffs from AU$150 vs four bearings @ trade $250).

Hope it helps,
G.

Yes, it was full of fluid, I did drain it before dropping it.

Something is wrong for sure... if not, then the diff shouldn't be nearly on fire when I come off track, smoking out of the overflow tube for a good 20 minutes with the diff housing measuring close to 400F. Now it sounds like straight cut gears and whistles at highway speeds. At 5-10 mph you can definetly hear something going on back there (bearing wise) when giving it gas.

I was hoping to find a pile of bearings or something very obvious when I opened the case, but didn't...

[mattah]

Hi Greg,

Great to see you on here. I was hassling you via PM before on Silvia WA about getting a HLSD set up for my S13. I've finally found the Z32 NA rear cover that I was talking about, but now that I've finally found it I don't know how necessary they are for HLSDs. The HLSD would usually put out a lot less heat than a VLSD or clutch type diff I would have thought? I guess it can't hurt to put the finned cover on anyway, it does give the extra oil capacity as well.

I'll be in touch shortly anyway!

[Dalspec]

Hi there,
I do recall
Definitely worth putting the larger cover on. Anytime I can reduce the load on oil and manage temperatures better, I try to. One look at the racing GTRs and the number of coolers they run says there's merit in it.
Cheers,
Greg

Hi Greg,

Great to see you on here. I was hassling you via PM before on Silvia WA about getting a HLSD set up for my S13. I've finally found the Z32 NA rear cover that I was talking about, but now that I've finally found it I don't know how necessary they are for HLSDs. The HLSD would usually put out a lot less heat than a VLSD or clutch type diff I would have thought? I guess it can't hurt to put the finned cover on anyway, it does give the extra oil capacity as well.

I'll be in touch shortly anyway!

[McCoy]

Thanks for the time spent on this response, and I am sure it's probably a side or pinion bearing, just thought I'd have a clearer indicator once I got the diff off the car.

I guess I'll answer your questions first.

1> Honestly can't answer these questions, I swapped the HLSD for the open diff 3 years back and everything felt the same after as it did before is the most I remember. The pinion bearing is the original (19 years, 190,000 miles) and the side bearings are what came with the HLSD.
2>will do that tonight if I don't get back to late
3>not that I could tell, no marks on the races to indicate so.
4>they seem to, both act the same, of course I'm not sure how good of judge of this I am.
5>Pinion turns freely and no play as I mentioned, but I don't have a known good example to compare it too.
6>no sign of wear of the pinion or ring, even took a closeup picture and looked it over on my computer.

I'll do a few more checks tonight, but will probably wait for the guys at the local tranny shop to do an inspection, they said they'd only charge me $20 to inspect it, so I'll probably take them up on it.

I build R200s so thought I'd chip in.

A few things I'd look at:
1. Comparison of backlash, pinion pre-load and ring-gear run-out to the figures measured when it was last built. ie when the torsen/helical was installed. Are they similar or different?
2. If the figures aren't available I'd measure it and compare to factory tolerances (I can almost guarantee pinion pre-load will be loose and backlash wil have opened up).
3. Is there evidence of the side bearing races having spun up in the housing?
4. Do the side bearings turn freely without binding?
5. Does the pinion turn freely without binding?
6. Is there clear evidence of tooth heel wear (outside drive face)? ie bearing blue/paste not requried to show wear?

My first guess (without more info), is pinion or side bearing bearing failure. As the bearing(s) fail the pinion and ring gear are allowed to walk away from each other. The teeth subsequently engage differently and results in whining under accel and decel and clunking on/off gas. Both get worse the longer it is left.

Replacement of both front bearings or the offending side bearing stops the clunking and whine if caught early enough. If not the whine remains, albeit lessened, as the wear pattern has changed.

More often than not, the ones I come across are bin jobs as 200s are cheap (here in Perth anyway), so it's more cost effective to transfer a centre to a new donor diff than replace bearings (Donor diffs from AU$150 vs four bearings @ trade $250).

Hope it helps,
G.

[Def]

If it were me, I'd just toss the HLSD into another S13 open diff and see what happens. I bet it fixes whatever the problem is. Other alternative is trying to find a 4.36 vlsd, but hard to do on short notice.

[McCoy]

Jacob, I'm going to look at both options. I agree the HLSD looks to be fine and it is probably the pinion gear if I was to guess, but who knows.

The great part about living in the wheat fields, no one is really close

[hai1206vn]

I'm quite sure that amount of play is really excessive. I remember clearly what .004" (spec) of backlash looks like when I had it shimmed and double checked myself with a dial. If you see the ring gear move in a blurry youtube video, it's certainly too much.

One thing you could do is to put the ring gear and diff assembly back in with shims. If they just fall in place easily without any hammering at all, your side bearings/races have worn too far, letting the ring gear move away from pinion. Proper size shims should require some tapping to seat in. Spinning the ring gear upward by hand should feel similar to lifting a gallon milk jug (that's 8lbs).

With the shavings you see on the drain plug, I'd just buy another rear end and swap the helical over with side bearings from the open diff. Buying new shims of various sizes can cost just as much.

Yea and the HLSD should be fine, most damage is usually in the main gear set.

Also, don't trust tranny shop guys with just a visual check. My old rear end had about that much play which they said was normal. These guys go by their truck & van experience, not tight Japanese crevices

[McCoy]

Got a local source for either an open diff (4.08) or a diff with a (4.3), probably going to go with the 4.3 if I can.

To get the diff back into the case takes a rubber mallet, so I know the sides gear/bearings are probably ok, I'm suspecting the pinion bearing actually... but doesn't matter as everyone has mentioned it's just cheaper to get a new diff and swap the HLSD over.

[McCoy]

Decided to go with option #3... GTR rear diff with a Nismo 4.6 R&P and the Nismo 1.5 way LSD. It's all local and comes with the axles, plug and play for the win.

I wanted to go with a 4.3 eventually, but maybe the 4.6 is a better option especially if I decide to go back to a 275 in the rear...

The $50 open diff started to get more expensive once you factor in $100 in new side bearings and $100 (est) to install them on the HLSD and I still have a 4.08 R&P. If I don't like the nismo LSD, then I'll swap it out later for the HLSD again.

[WorkInProgressK]

isnt the nismo a normal clutch type LSD?

If so you will like to be able to pivot slightly the car by just letting go of the gaz.

Steering correction with the right foot FTW.

[Matt93SE]

Wanna hook me up with that 4.3 you didn't use?

[McCoy]

isnt the nismo a normal clutch type LSD?

Yep, 1.5-way from what I read everywhere. I have nothing bad to say about the HLSD, but would like to try this and know for myself which I'd prefer to go with long term.

Wanna hook me up with that 4.3 you didn't use?

Ebay... GTR housing, 4.3 gears, Nismo 2-way (probably a 1.5-way) diff.